Grand-canonical ensemble of random surfaces with four species of Ising spins.

The grand-canonical ensemble of dynamically triangulated surfaces coupled to four species of Ising spins ([ital c]=2) is simulated on a computer. The effective string susceptibility exponent for lattices with up to 1000 vertices is found to be [gamma]=[minus]0.195(58). A specific scenario for [ital c][gt]1 models is conjectured.